The N.C. Supreme Court’s ruling upholding the state’s “Opportunity Scholarships” program cements North Carolina’s status as one of 14 states with voucher programs that use taxpayer dollars to pay private school tuition.

The court’s decision comes at a time when the General Assembly is debating expanding the voucher program. Last year the legislature provided almost $12 million for vouchers, and under both the House and Senate budgets this year that would increase to nearly $18 million.

The court’s ruling explains that the decision was limited to whether constitutional requirements are met. Beyond that, the court explains, “the wisdom of the legislation is a question for the General Assembly.” With the constitutional question resolved, the legislature’s evaluation of whether to continue or expand the current program should depend on how vouchers affect students and schools – both those whose students receive the vouchers and those whose don’t.

Studies on voucher programs’ effects on student performance have mixed results. To date, the most rigorous research has failed to show strong evidence of sustained, improved academic performance for students using vouchers, though some studies have demonstrated links between vouchers and improved performance for specific demographic groups. Differences in how voucher programs are implemented from state to state also hamper the ability of researchers to draw solid conclusions about program impacts.

Voucher supporters have theorized that the programs’ benefits would stretch beyond students receiving vouchers by creating competition that would force public schools to “up their game.” Here, too, the research is hazy. Studies of test scores in Florida 2007-2010 showed a correlation between improved test scores in the lowest-performing schools and the availability of vouchers. However, during the time period studied, Florida undertook a bevy of education reforms, any of which might have caused the observed changes in test scores.

The lack of conclusive research on voucher effectiveness should give North Carolina pause. Without a clear model to emulate, or best practices to implement, the state should proceed with caution in expanding its voucher program.

Under the law upheld Thursday, North Carolina has some guidelines in place to implement the state’s voucher program in a measured way. First, only students with household incomes under 133 percent of the free and reduced lunch price guidelines are eligible. This reflects a concerted effort to serve students who stand to gain the most financially from the voucher program. Second, to begin receiving vouchers, students must be entering kindergarten or must have attended a public school the previous semester. This requirement keeps the focus of the program on families who do not believe their children’s educational needs were adequately met in their public schools, rather than those who never attended (or intended to attend) public schools in the first place.

With the constitutional obstacles cleared in North Carolina, there will certainly be those who argue for expansion beyond these established limits. In some states – Wisconsin, for instance –efforts are under way to relax voucher rules to permit students at higher income levels or those already enrolled in private schools to participate.

As state leaders look ahead, they should balance the voices calling for significant expansion with the broader realities of North Carolina’s public education funding. Per-pupil funding continues to lag behind pre-recession levels, textbook funding is almost $40 million lower than it was in 2009, and average teacher pay, despite last year’s increases, continues to rank in the bottom 10 nationally. Deep cuts have left the state with 7,000 fewer teacher assistants in grades K-3 than we had in 2008, in spite of a heightened emphasis on third-grade reading levels. This year’s Senate budget would cut 8,500 more TA jobs. And teachers in our public schools often find themselves fundraising online or buying basic school supplies out of their own pockets. In that context, an initiative that pulls more funding out of our public schools at precisely the moment when they need most to be built back up ought to be thoughtfully debated.

The current law directs private schools accepting vouchers to administer state assessments (or their equivalent), report voucher students’ graduation rates, provide parents with annual assessments that include standardized test scores and, when more than 25 voucher students attend a school, report their aggregate test scores. What’s not clear is what will be done with this information. Will the state play a role in determining which schools are fit to receive vouchers? If it doesn’t, will money simply end up being transferred from struggling public schools to struggling private schools? How can North Carolina parents be confident that schools they choose for their children to attend using vouchers will offer a superior education?

If the state’s goal is truly to provide a world-class education for every child in North Carolina, then the legislature would be wise to expand the voucher program slowly and only upon the establishment of a solid base of evidence that the program improves educational outcomes for North Carolina’s most disadvantaged students.